The crystalline lens of the human eye refracts and focuses light onto the retina. Normally the lens is clear, but it can become opaque (i.e., when developing a cataract) due to aging, trauma, inflammation, metabolic or nutritional disorders, or radiation. While some lens opacities are small and require no treatment, others may be large enough to block significant fractions of light and obstruct vision.
Conventionally, cataract treatment involves surgically removing the opaque lens matrix from the lens capsule using, for example, phacoemulsification and/or a femtosecond laser through a small incision in the periphery of the patient's cornea. An artificial intraocular lens (IOL) can then be implanted in a lens capsule bag (the so-called “in-the-bag implantation”) to replace the crystalline lens. Generally, IOLs are made of a foldable material, such as silicone or acrylics, for minimizing the incision size and required stitches and, as a result, the patient's recovery time. The most commonly used IOLs are single-element lenses (or monofocal IOLs, non-accommodating IOLs, non-focusing IOLs) that provide a single focal distance for distance vision. Typically, distance vision requires limited contraction of ciliary muscles in the eye (i.e., Emmetropia); thus monofocal IOL designs are relatively simple. For example, to choose an appropriate geometry for a monofocal lens having a desired focusing power, limiting factors of the eye's anatomy, such as the axial eye length and the power of the cornea, are taken into consideration. However, because the focal distance is not adjustable following implantation of the monofocal IOL, patients implanted with monofocal IOLs can no longer focus on objects at a close distance (e.g., less than twenty-five centimeters); this results in poor visual acuity at close distances.
Recently, accommodating intraocular lenses (AIOLs) have been developed to provide adjustable focal distances (or accommodations) relying on the natural focusing ability of the eye. Because an AIOL works closely in coordination with the eye tissue, the focusing power thereof is sensitive to the geometric properties of the eye tissue. For example, ciliary muscles of the eye may contract, causing a change in the diameter and/or the shape of the lens capsule accommodating the AIOL; this results in an adjustment of the focal distance. Additionally, the shorter the focal distance of the AIOL, the more sensitive the AIOL will be to a change in geometry of the eye tissue. Because the anatomic geometry of the human eye may change with age and behavior, and geometric variances exist among people, it remains challenging to determine an appropriate geometry of the AIOL for each specific patient to satisfy her unique needs.
Consequently, there is a need for methods and systems for determining an AIOL geometry that can provide a high degree of accommodation and desired focusing power for a given individual.